Veritas Storage Foundation 5.0.1 Cluster File System Administrator's Guide Extracts for the HP Serviceguard Storage Management Suite on HP-UX 11i v3

NOTE: The master/slave node naming convention continues to be used when referring to
Veritas Cluster Volume Manager (CVM) nodes.
Cluster File System Failover
If the server designated as the CFS primary node fails, the remaining nodes in the cluster elect
a new primary node. The new primary node reads the intent log of the old primary node and
completes any metadata updates that were in process at the time of the failure.
Failure of a secondary node does not require metadata repair, because nodes using a cluster file
system in secondary mode do not update file system metadata directly. The Multiple Transaction
Server distributes file locking ownership and metadata updates across all nodes in the cluster,
enhancing scalability without requiring unnecessary metadata communication throughout the
cluster. CFS recovery from secondary node failure is therefore faster than from primary node
failure.
Group Lock Manager
CFS uses the Veritas Group Lock Manager (GLM) to reproduce UNIX single-host file system
semantics in clusters. This is most important in write behavior. UNIX file systems make writes
appear to be atomic. This means that when an application writes a stream of data to a file, any
subsequent application that reads from the same area of the file retrieves the new data, even if
it has been cached by the file system and not yet written to disk. Applications can never retrieve
stale data, or partial results from a previous write.
To reproduce single-host write semantics, system caches must be kept coherent and each must
instantly reflect any updates to cached data, regardless of the cluster node from which they
originate. GLM locks a file so that no other node in the cluster can simultaneously update it, or
read it before the update is complete.
VxFS Functionality on Cluster File Systems
The HP Serviceguard Storage Management Suite uses the Veritas File System (VxFS). Most of
the major features of VxFS local file systems are available on cluster file systems, including:
• Extent-based space management that maps files up to 1 terabyte in size
• Fast recovery from system crashes using the intent log to track recent file system metadata
updates
• Online administration that allows file systems to be extended and defragmented while they
are in use
Supported Features
The following table lists the features and commands that are available and supported with CFS.
Every VxFS online manual page has a Cluster File System Issues section that informs you if the
command functions on cluster-mounted file systems, and indicates any difference in behavior
from how the command functions on local mounted file systems.
Table 1-1 CFS Supported Features
Features and Commands Supported on CFS
The clusterized Oracle Disk Manager (ODM) is supported with CFS using the Quick I/O for
Databases feature in the following HP Serviceguard Storage Management Suite CFS bundles
for Oracle on HP-UX 11i v3: T2777DB, T8686DB, T8687DB, T8696DB, and T8697DB
Quick I/O
Storage Checkpoints are supported with CFS.Storage
Checkpoints
10 Technical Overview